Hermetic
Is hermetic the same as waterproof?
No. Hermetic means gas-tight and resistant to moisture and gases, while waterproof usually refers to liquid water resistance and does not necessarily guarantee long-term gas impermeability.
How is hermeticity verified in production?
Common methods include helium leak testing with acceptance criteria based on the allowed leak rate for the package volume. MIL-STD-883 Method 1014 is widely referenced for microelectronic packages.
Why can a part pass dimensional inspection and still fail hermetic testing?
Hermeticity depends on the integrity of the entire leak path, not only on nominal dimensions. Microscopic surface defects, porosity, or interface mismatch can allow permeation or leakage even when measurements are within tolerance.
Hermetic means sealed so tightly that no air, gas, or moisture can enter or escape. In technical manufacturing, it refers to an airtight, gas-tight seal rather than a generic tight fit. Hermeticity is the condition of maintaining that barrier over time, commonly verified by helium leak testing, with MIL-STD-883 Method 1014 used to classify a package as hermetic or a leaker.
On the shop floor, hermetic requirements change how a machinist approaches sealing faces, joint interfaces, and assembled enclosures. A part may hold nominal dimensions yet still fail a helium leak test if the seal path contains a continuous micro-leak. Tool marks, chatter, burrs, porosity, flatness error, or out-of-round holes can all break the gas-tight barrier. When machining housings, connectors, glass-to-metal seals, or precision enclosures, the goal is not just a tight fit but a matched, defect-free surface that maintains vacuum, pressure, or contamination control. This means paying attention to cutting parameters, deburring, and material pairing, especially where metals, ceramics, and glass are joined. Thermal cycling can open cracks if coefficients of expansion are mismatched. In practice, hermeticity is verified by leak testing rather than by calipers, and the entire joint, weld, braze, gasket, or bonded interface must be treated as a single continuous barrier.
Airtight illusion: A part can be fully assembled and still fail hermeticity when micro-gaps, capillary paths, or porous material defects let gas migrate through the interface over time. Mechanical closure alone does not guarantee a continuous gas-tight barrier.
Chatter-scarred seal land: Tool chatter, burrs, scratches, or poor deburring on a sealing face break the contact line and concentrate stress, creating micro-leaks that pass visual inspection but fail helium leak testing later.
Thermal mismatch cracks: Hermetic assemblies often pair metals, ceramics, or glass with different expansion rates. Repeated temperature swings can crack the seal, open micro-leaks, or degrade the interface even when the original machining was perfect.